Chlamydia trachomatis (=C.t.) causes more than four million cases of sexually transmitted disease annually in the United States. Antibiotic treatment has not significantly reduced dissemination of C.t. and manipulation of the immune system with vaccines or other means may prove to be the best way of reducing case load and pathogenesis. Toward this end, the broad goal of the proposed work is to isolate and characterize T cell lines and clones from C.t-infected humans. The initial outgrowth of such T cells from peripheral blood will be stimulated with C.t. elementary bodies (=EBs) or lysates thereof and with purified MOMP, an immunodominant major outer membrane protein. The antigens will be presented by either autologous peripheral blood antigen-presenting cells (=APC) or by permanent cell lines derived form macrophages, endometrial- epithelial or B cells. Attempts will be made to detect antigen processing in exogenous and endogenous pathways. C.t.-response T cell clones will be derived early and characterized with regard to functional type and the HLA molecule each clone recognizes in association with a C.t. epitope. MOMP epitopes that are presented with specific HLA molecules will be identified by testing responsiveness of T cell clones to a collection of 25 amino acid-long synthetic peptides that have overlapping sequences spanning the MOMP sequence and that are presented by B cell APC lines that uniquely express the HLA molecule being tested. A search for non-MOMP antigens will be made by resolving total EB proteins by gel electrophoresis and isolating T cell lines or clones that respond to specific protein fractions. These T cells will also be characterized with regard to functional type and HLA specificity. Further protein fractionations will be used to identify the specific C.t. antigens using the characterized T cell clones as reagents.